Relief valves are usually mounted on the intermediate casing of the turbomachine, between the low-pressure compressor and the high-pressure compressor, in an annular space extending between the main flow stream and the bypass flow stream.
These relief valves are evenly distributed about the longitudinal axis of the turbomachine and each comprise a gate that can be moved relative to the intermediate casing, between a closed position of an orifice for the passage of air formed in the intermediate casing and an open position of this orifice. The opening of these gates makes it possible to discharge a portion of the main air flow in certain operating conditions of the turbomachine, this air being reinjected into the bypass flow or supplying systems for cooling or ventilating components of the turbomachine.
In certain embodiments, the gates of the relief valves have a substantially parallelepipedal shape and the corresponding orifices of the intermediate casing have a shape that matches that of the gates. An elastomer seal that is generally U-shaped extends along the peripheral side and downstream edges of each gate and is designed to interact with a matching portion of the edge of the orifice of the intermediate casing in order to provide the seal around the gate in its position of closure of this orifice.
In the prior art, this seal is attached to the gate by means of a U-shaped plate which is fitted to the seal and which is attached to the gate by rivets passing through the seal. The seal is therefore kept clamped onto the peripheral edge of the gate. The gate and the plate are usually made of metal, for example of aluminium.
Each gate comprises pivoting means formed by lugs which extend from an upstream end portion of the gate radially outwards. These lugs comprise at their radially inner ends coaxial cylindrical bores for mounting bearings for centring and guiding a first pivot supported by the intermediate casing, and defining the pivoting axis of the gate. These lugs also comprise at their radially outer ends coaxial cylindrical bores for mounting bearings in which a second pivot is engaged, mounted at the end of a link rod which controls the pivoting of the gate about the first pivot. The bearings mounted in the bores of the lugs are usually made of steel or polymer.
This relief valve therefore comprises a relatively high number of components (twenty five in total in one particular embodiment: a gate, four bearing bushes, a seal, a plate for attaching the seal, nine rivets, and nine spacers), which results in a relatively high weight and cost, the manufacture and assembly of these various parts being relatively long.